Method and apparatus for producing multicomponent filaments and yarns



April 28, 1970 T. c. BoHRER 3,509,248

ME D AND APPARATUS FOR PRODUCING MU COMPONENT FILAMENTS AND YARNS Uriginal Filed March 2, 1966 V//IW////Z INVENTOR mon/: 5 5o/M75@ ATTORNEYS United States Patent O 3,509,248 METHOD AND APPARATUS FOR PRODUC- ING MULTICOMPONENT FILAMENTS AND YARNS Thomas C. Bohrer, Madison, NJ., assignor to Celanese Corporation, New York, N.Y., a corporation of Delaware Continuation of application Ser. No. 531,250, Mar. 2, 1966. This application Dec. 24, 1968, Ser. No. 788,688 Int. Cl. B29f 3/10; D01d 11/06 U.S. Cl. 264-171 9 Claims ABSTRACT F THE DISCLOSURE Process and apparatus for producing multicomponent filaments having a sheath/core configuration are described.

This a continuation of Ser. No. 531,250 filed Mar. 2, 1966.

This invention relates to multicomponent filaments and, more particularly, to a method and apparatus for spinning multicomponent filaments.

One type of multicomponent filament has a sheath of one material that is formed around a core of another material. Such bilaminar filaments have unique properties. For example, a high strength polymer may be used for the core and a polymer of desirable surface characteristics might be used for the sheath to produce a filament having high strength properties combined with a good appearance. Also, an inexpensive core fiber of relatively inferior properties might be encased in a sheath of high cost polymer that has the desired characteristics, in order to achieve a filament having a substantially lower cost than if it were made entirely out of the expensive polymer. Also, a polymer having favorable hand and dye characteristics may be used as a sheath on a core of relatively inexpensive polymer having good mechanical properties.

Accordingly, it is an object of this invention to provide a method and apparatus for producing multicomponent filaments.

It is another object of this invention to provide a method and apparatus for efficiently spinning multicomponent filaments.

A further object of this invention is to provide a method and apparatus for drying spinning continuous filaments having a core of one plastic material that is enclosed in a sheath of another plastic material.

These objects are accomplished in accordance with a preferred embodiment of the invention by extruding from an orifice a stream of core dope through a body of sheath dope and then passing the composite stream through a smaller orifice. Preferably, the stream of core dope flows at a sufficiently low velocity in relation to the viscosity and density, so that the stream is in laminar flow. At the interface between the stream of core dope and the sheath dope, flow is induced in the sheath dope, b ut the sheath dope does not mix with the core dope. There is suflicient spacing between the core dope orifice `and the composite stream orifice for the core stream to be employed in a moving film of sheath polymer. In passing through the outer orifice, the composite stream is attenuated without interrupting the sheath coating or the dope. Preferably, the process of this invention is carried out using dry spinning techniques.

This preferred embodiment of the invention is illustrated in the accompanying drawings in which:

FIGURE l is a schematic View of apparatus for dry spinning incorporating the jet assembly of this invention;

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FIGURE 2 is a cross sectional view of the jet assembly;

FIGURE 3 is an enlarged cross sectional view of the jet assembly;

FIGURE 4 is a cross sectional view along the line 4-4 in FIGURE 2; and

. FIGURE 5 is a cross sectional view of a multicomponent filament produced in accordance with this invention.

In producing filaments by dry spinning processes, the polymer is carried in a solvent solution and extruded through a spinneret or jet assembly. Referring to FIG. l, a sheath polymer solution is conducted under pressure through the pipe 2 into the jet assembly 4 and a core polymer solution is conducted through the pipe 6 into the jet assembly. The lower portion of the jet assembly is enclosed in a chamber 8 and a stream of heated gas is conducted into the chamber through an inlet pipe 10 and the gas passes out of the chamber through an outlet pipe 12. The polymer solutions are extruded from the jet assembly 4 in the form of filaments 14 which pass over a roller 16, from which they are guided out through the wall of the chamber 8. The rapid flow of gas through the chamber evaporates the solvent from the polymer solutions as the filaments are extruded by the jet assembly 4.

The jet assembly includes a casing 18, as shown in FIG. 2, having a fitting 20 threadedly secured by a nipple 22 to one end of the casing 18. The fitting 20 has an inner spinneret 24 and an outer spinneret 26 secured to the end of the fitting by a threaded ring 28. The inner spinneret 24 is substantially circular and has a threaded washer 30 secured at its center. A tube 32 is threaded into the washer 30 and extends through the spinneret 24. A nut 34 is also threaded on the tube 23 and is jammed against the washer 30 to lock the tube in position.

At the opposite end of the casing 18, a plug 36 is threaded into the end of the casing. The plug 36 has a central opening through which the tube 32 extends. The end of the tube 32 is connected to the tube 2 by a conventional coupling. The tube 32 is positioned substantially centrally of the interior passages through the fitting 20 and the casing 18. The spinneret 24 has substantially the form of a frustum of a cone and has an outwardly projecting flange 36. The outer spinneret 26 also has an outwardly projecting flange 40. There are gasket rings 42 between the flanges 38 and 40 and the rings 42 are compressed between the end of the fitting 20 and a flange 44 on the threaded ring 28.

As shown in FIG. 4, thel inner spinneret 24 has a plurality of equally spaced orifices 46. A corresponding number of orifices 48 are provided in the outer spinneret 26 and the orifices 48 are positioned in alignment with the orifices 46 in the inner spinneret. An alignment pin 50 having one end rigidly secured in the fitting 20 passes through holes in the flanges 38 and 40 when the spinnerets 24 and 26 are assembled together to ensure that the orifices in the spinnerets are aligned.

The polymer solution or dope that is used for the core of the filaments in conducted through the pipe 6 through the casing 18 and through the fitting 20 to the interior of the spinneret 24 where it is confined between the spinneret 24 and the fitting 20. The polymer solution or dope for the sheath around the core is conducted under pressure through the pipe 2 into the space between the inner spinneret 24 and the outer spinneret 26. As shown in FIG. 3, the core dope flows outwardly through the orifices 46 in a steram that is confined by the sheath dope between the spinnerets 24 and 26. The outer orifices 48 are substantially smaller than the orifices 46, causing attenuation of the streams 50 as they pass through the orifices 48. Since the streams 50 are in laminar flow, the sheath dope surrounding each stream does not mix with the core dope, but flows toward the orifice 48 in a film surrounding the stream at the surface. When the composite streams 50 emerge from the orifices 48, the gas in the chamber 8 rapidly evaporates the solvent in the core dope and the sheath dope forming continuous filaments 14.

The orifices 46 and 48 preferably have a substantially constant diameter and are unobstructed by shoulders or other projections which would disturb the laminar fiow of the streams 50 through the spinnerets 24 and 26. Furthermore, the interior of the spinnerets 24 and 26 around each of the orifices extends substantially at right angles to the axis of the orifices in order to minimize turbulence.

A typical filament is shown in cross section in FIG. 5.

The lament 14 has a central portion 52 of the polymer in the core dope and an outer portion 54 that is formed of the polymer in the sheath dope. The sheath portion 54 entirely encloses the central portion 52.

In operation, core dope is supplied through the pipe 6 to the jet assembly and skin dope is supplied through the tube 2 to the jet assembly until the spinnerets 24 and 26 are filled with dope, as shown in FIG. 2. Fluid pressure is then applied to the core dope in the tube 6 to cause extrusion of the core dope through the orifices 46 in the inner spinneret 24. The fiuid pressure is adjusted so that the core dope stream passes from the inner spinneret 24 to the outer spinneret 26 in laminar flow and the process continues as long as core and sheath dope are supplied to the jet assembly.

The viscosity of the sheath dope should be approximately the same or less than the viscosity of the core dope 4in order to ensure the proper formation of the stream 50. Generally, the amount of polymer dissolved in the solvent should be between about 8 and 35 percent by weight, but preferably within the range between and 30 percent by weight. Polymers that may be used in the spinning dopes include secondary cellulose acetate, cellulose triacetate, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl acetate, polycarbonates, polyolefins, polyesters, polya-mides, po-lyurethanes and polyureas.

As a specific example of the process and apparatus of this invention, one inch, five hole spinnerets were used for the inner and outer spinnerets 24 and 26. The diameter of the orifices in the outer spinneret was 56 microns (.056 millimeter) and the diameter of the orifices for the inner spinneret 24 was 100 microns (.100 millimeter). The approximate distance between the two spinnerets 24 and 26 was 716 of an inch. Bright and pigmented cellulose triacetate spinning dopes were used for purposes of demonstration. The cellulose triacetate was dissolved in a mixture of methylene chloride and methanol to produce spinning dopes containing about 22 percent solids. The pigmented dope also contained about 1.25 percent titanium dioxide. The pigmented dope was used for the sheath and the bright dope was used for the core. Both of the dopes were approximately fifteen hundred poises viscosity at 25 C. The filaments produced had a central portion of bright cellulose triacetate and an outer portion of pigmented cellulo-se triacetate, substantially as shown in FIG. 5.

The axial distance separating an orifices in the inner spinneret and the corresponding orifice in the outer spinneret is between 25 and 50 times the diameter of the inner orifice. The diameters of the orifices in either the inner or outer spinnerets are between 30 and 150 microns.

One important advantage of the apparatus and method of this invention is that conventional jet assemblies can be converted for producing bilaminar filaments with a minimum of expense and retooling. For example, conventional spinnerets could be used for the inner and outer spinnerets 24 and 26, with the inner spinneret having a hole drilled at the center to receive the tube 2. Instead of the complex jet structures that are found in the prior art, the apparatus of this invention is relatively simple in construction, and yet produces a multicomponent filament.

While this invention has been illustrated and described in one embodimennit is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.

I claim:

1. A process for producing multicomponent filaments comprising extruding core dope through a first orifice into a body of sheath dope, said sheath dope confining said core dope in a stream in laminar flow condition, attenuating said stream by drawing through a second orifice without interrupting said laminar flow conditions, said second orifice having a diameter less than that of said first orifice, and subsequently solidifying said dopes to form a multicomponent filament, the distance between said first and second orifices being between 25 and 50 times the diameter of said first orifice and the diameters of said first and second orifices being -between 30 and 150 microns.

2. The process according to claim 1 wherein the viscosities of said core dope and sheath dope are about 1500 poises at 25 C.

3. The process according to claim 1 wherein said core dope and sheath dope contain cellulose triacetate.

4. Apparatus for producing multicomponent filaments comprising wall means forming a first chamber and a second chamber separated by a partition, means for conducting core dope to said first chamber, means for conducting sheath dope to said second chamber, said partition having a first orifice therein, said wall means having a second orifice therein in substantial axial alignment with said first orifice, said orifices being spaced apart a distance greater than the diameter of said first orice, the diameter of the second orifice being smaller than the diameter of the first orifice, said first and second orifices being separated by a distance equal to between 25 and 50 times the diameter of said first orifice, the diameters of said first and second orifices being between 30 and 150 microns.

5. The apparatus according to claim 4 wherein said wall means includes a pair of discs secured at their periphery to a housing and said sheath dope conducting means including a tube extending through the housing and through one of said discs.

6. The apparatus according to claim 5 wherein said core dope conducting means includes a passage through the housing around said tube.

7. The apparatus according to claim 5 wherein said first one disc has said first orifice and the other disc has said second orifice.

8. The apparatus according to claim 5 wherein said housing is cylindrical and has an open end, said discs being secured over said open end by ring means engaging the periphery of said discs.

9. The apparatus according to claim 5 including gas circulating means adjacent said second orifice on the outside of said wall means.

References Cited UNITED STATES PATENTS 3,341,891 7/1967 Shimizu et al.

FOREIGN PATENTS 514,63 8 ll/1939 Great Britain.

628,679 10/1961 Canada.

DONALD I ARNOLD, Primary Examiner I. H. WOO, Assistant Examiner U.S. Cl. X.R. 18-8 

